1. Field of the Invention
This invention relates to DC-DC converters and, in particular, to a circuit for detecting the reduction in power supplied to a converter.
2. Description of the Prior Art
When the power from a resistive source supplied to any converter is decreased, thereby decreasing the voltage at the input to the converter, the width of the drive pulse to the switching transistor will be increased in attempting to increase the duty cycle (or ON time) of the switching transistor. It is necessary to know when there is such a decrease in power supplied to the converter so that the load on the converter may be reduced.
In the prior art, the decrease in input power is determined by detecting when the output current from the converter exceeds a predetermined threshold value corresponding to full load, namely, the maximum duty cycle of the switching transistor. The disadvantage with the prior art lies in detecting the input power reduction after full load has been reached. It is necessary to know when there is an input power reduction before full load is reached, particularly in a large parallel DC-DC converter system, so that the load on the converter system may be reduced, thereby preventing system failure.